As a nonvolatile semiconductor memory device, a flash memory device which stores information in a non-volatile manner by storing a charge in a charge storage layer such as a floating electrode or a trap layer, for example, has been developed. The nonvolatile semiconductor memory device includes a memory element which stores information in a non-volatile manner, and a peripheral element, which is an element other than the memory element. Examples of the peripheral element include a select transistor for selecting a memory element for reading thereof, writing thereto, or erasing thereof, and a transistor configuring a peripheral circuit for driving, i.e., providing a charge to, the memory element.
To achieve high speed writing and erasing of the memory elements, the gate electrode resistance must be low. For ease and simplicity of manufacturing, the memory element and the transistor of the peripheral circuit are often formed at the same time. However, the gate electrode of each element has a different optimal structure for the memory element transistors as compared to that for the transistor of the peripheral circuit.